DOC-4687 DOC-4749 Added OS upgrade module known limitation to 7.8.4 release notes

Author: rrelledge

content/operate/rs/release-notes/rs-7-8-releases/_index.md

@@ -234,6 +234,12 @@ The following table provides a snapshot of supported platforms as of this Redis
 
 ## Known limitations
 
+#### Upload modules before OS upgrade
+
+If the cluster contains any databases that use modules, you must upload module packages for the target OS version to a node in the existing cluster before you upgrade the cluster's operating system.
+
+See [Upgrade a cluster's operating system]({{<relref "/operate/rs/installing-upgrading/upgrading/upgrade-os">}}) for detailed upgrade instructions.
+
 #### New Cluster Manager UI limitations
 
 The following legacy UI features are not yet available in the new Cluster Manager UI:

content/operate/rs/release-notes/rs-7-8-releases/rs-7-8-4-tba.md

@@ -116,6 +116,12 @@ The following table shows the SHA256 checksums for the available packages:
 
 ## Known limitations
 
+#### Upload modules before OS upgrade
+
+If the cluster contains any databases that use modules, you must upload module packages for the target OS version to a node in the existing cluster before you upgrade the cluster's operating system.
+
+See [Upgrade a cluster's operating system]({{<relref "/operate/rs/installing-upgrading/upgrading/upgrade-os">}}) for detailed upgrade instructions.
+
 #### New Cluster Manager UI limitations
 
 The following legacy UI features are not yet available in the new Cluster Manager UI: